semiperiod edge trigger

[Olivier B.]

Hello,
I am using a PXI 6602 (to wait for a PXI6624) card with Labwindows and Daqmx 7.3 to perform semiperiod PWM signal measurement to retrieve the duty cycle of an input signal.
DAQmx assistant works well : when choosing buffered semiperiod measurement, I retrieve a table containing duration of all levels of my signal on GATE input.

My problem is : how to know what was the level (logic sate : 0 or 1) of my signal when the card started counting ?
The daqtask must be defined as continuous sampling.

I tried to find a way to associate an active edge detection for GATE input, but was unable to make it work...

Would you please have a solution ?

Olivier.

[gus]

Hello Olivier-

Please check this thread concerning semiperiod measurement issues.

Configuring an arm start trigger in CVI can be done with the following function calls:

DAQmxSetArmStartTrigType()
DAQmxSetDigEdgeArmStartTrigSrc()
DAQmxSetDigEdgeArmStartTrigEdge()

and you'll want to pass your input signal as the trigger source. The trigger edge will tell you whether you begin measuring on rising or falling edges.

I hope this helps!
gus....

[Olivier B.]

Thanx gus for your quick answer. I ve already read the issue about semi period you mention, but it was a labview issue.

I can t find the function panels for the function:
DAQmxSetArmStartTrigType()
DAQmxSetDigEdgeArmStartTrigSrc()
DAQmxSetDigEdgeArmStartTrigEdge()
In daqmx 7.3.0.f0. Do i need to upgrade the ni daqmx driver?
Thank u for your support.
Olivier